Portable communicators, such as cell phones, sometimes use antennas with multiple radiators to enable phones to receive two different signal bands. These phones are compatible then with multiple cellular networks or different frequency services of a single cellular network. Such an antenna includes a first frequency radiator and second radiator which are alternately utilized through mechanical switching methods in typical devices. Frequently, one radiator might be active in a retracted position and another in an extended position.
Known techniques for connecting radiators to phone circuit contacts in such antennas include soldering and crimping to electrically connect radiators to electrodes or similar means which electrically couple to circuits of the portable communicators. A problem exists in that techniques such as soldering and crimping change the electrical characteristics of the antenna in a manner which may vary from one manufactured antenna to the next. For example, the process of adding solder to the antenna is an inherently imprecise venture since the solder adds variable amounts materials to the radiators which change the electrical characteristics of one manufactured antenna to the next. Additionally, crimping is not a desired technique since crimping can cause the radiator to deform, thus adversely affecting the electrical characteristics of the antenna. The latter problem is typically experienced when the pitch of a helical radiator is altered due to mechanical deformation during attachment.
Compensation for these variances is often achieved through additional processing, such as testing and trimming to tune the antenna to a desired frequency. Obviously, this increases both the cost and difficulty of manufacturing the antennas. In addition, operations such as soldering and crimping require assembly technicians skilled enough to perform the delicate and time-consuming techniques. Additionally, performance tolerances must be generous enough to accommodate the variances experienced in those antennas which are still suitable for use. Even so, a significant percentage of manufactured antennas may be unsuitable for use.
Related difficulties relate to high part counts and overall device complexity. It is generally desirable to reduce part counts because of the obvious benefits that such reduction has on manufacturing. In typical multiple band antennas, high part counts are often associated with the switching and connecting mechanisms to activate separate radiators for operation in separate bands.
Operation of known multiple band antennas is also limited since their structure typically requires some operator movement of the antenna to activate one radiator for one band of operation and deactive its other radiator for another band of operation. This conflicts with a trend in the art towards small fixed antennas, referred to as "stubbies". It also limits usefulness of the antennas since one band's operation is mutually exclusive of the other band's operation.
There is therefore a need for an improved portable communicator antenna which addresses problems in such known antennas. It is an object of the invention to provide an antenna which meets this need.